The present invention relates to computing installations likely to incorporate several computers operating independently intended to be associated with input or output terminal units (such as card readers, disk units, printers, modems, . . . ). In present installations, each independent computer is provided with terminal units which are assigned to it, even when each of these terminal units was able to be used possibly through an adapter, with any one of the computers. Devices are however known for mechanically switching one terminal unit to one or other of the computers so as to fulfil the requirements for a particular computing program. This mechanical switching has switching defects inherent in the technology and, in addition, is very ill suited to the random nature of the requirement of connecting different computers to a given terminal unit.